The CEO of Target apologized to the public for slower call center and website access and is now offering a 10 percent discount to all customers after a massive data breach left information of about 40 million shoppers vulnerable to thieves.

In his message, Target CEO Gregg Steinhafel said on Friday that the issue of unauthorized access to payment card data at their U.S. stores "has been identified and eliminated," and not all customers who shopped between Black Friday and last week are victims of fraud.

"Most importantly, we want to reassure guests that they will not be held financially responsible for any credit and debit card fraud. And to provide guests with extra assurance, we will be offering free credit monitoring services. We will be in touch with those impacted by this issue soon on how and where to access the service."

Target said that if a customer notices charges they did not make in their credit or debit account, they should contact the company at 1-866-852-8680. Otherwise, customers do not need to call, Target said, adding that the company will never ask a guest for their social security or pin number.

Steinhafel apologized to guests who tried to reach Target via its website or call center while it faces "unprecedented call volume." To ease the public's perception of Target, Steinhafel is offering a 10 percent in-store discount to customers in a single transaction on Saturday and Sunday.

"It was a crime against Target, our team members, and most importantly, our guests," he said in his statement. "We're in this together, and in that spirit, we are extending a 10 percent discount – the same amount our team members receive – to guests who shop in U.S. stores on Dec. 21 and 22."